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Tuesday, January 29, 2013

What's Your Trigger?

The Gist: "Permissive _____" is becoming increasing popular in medicine-blood glucose, blood pressure, and oxygen saturation. Hemoglobin is similar, but common refrains may be heard "well, he looks puny, let's give him a couple of units." Currently, the best evidence suggests that transfusion of packed red blood cells (PRBCs) should be considered in most critically ill medical patients, in the absence of massive hemorrhage, at a hemoglobin (hb) <7 g/dL. The data show that liberal transfusions don't benefit the patient and may harm them. However, there are limitations to the data and it and should be interpreted within the context of the individual patient. Treat the patient, not the lab value! Prevent iatrogenic anemia, resulting in more transfusions. Excellent review article from Annals of Intensive Care

The case(s): In the ED, transfusion of PRBCs is often clear-cut. Massive hemorrhage with high TASH score? Activate the protocol. Patient with melena, as white as the sheets, with a hemoglobin of 4.0 g/dL? Hang the blood. What about the 60 year old patient with suspected sepsis, resting comfortably without complaints, who has a hemoglobin of 7.8 g/dL (baseline ~8-8.5 g/dL)? What if we know he is undergoing fluid resuscitation due to the sepsis, borderline hypotension, and tachycardia, which will likely cause a dilutional drop in hemoglobin?I recently encountered similar cases and found the art of medicine plays a large role when patients. Tintinalli recommends transfusion at 7.0-9.0 g/dL, but our patient, like many, falls within that grey area so any course of action is justified (Ch 146). Can the literature help sort this out?

For similar degrees of organ dysfunction, patients who had a transfusion had a higher 28-day mortality rate 22.7% vs 17.1% (p =.02) in a matched patients in the propensity analysis

Higher mortality in ICU patients receiving PRBC transfusion (OR of death of 1.37).

Limitation: observational, although analysis accounted for degree of organ dysfunction, provider discretion played a role in decision to transfuse; thus, the sicker patients likely received more transfusions.

Upon mulivariate analysis, the number of PRBCs a patient received was independently associated with longer ICU and hospital LOS and an increase in mortality 1.65; 95%CI 1.35–2.03, p <.001). Note: one model showed increased mortality in patients with hb nadir <9.0.

Lower 30-day hazard of death in the transfused group when adjusted (HR 0.73; 95% CI 0.59–0.90; P <0.004)

Why the difference from the very similar ABC study?

Used more leukodepleted blood than the ABC study. This is now standard practice.

More knowledge about potential harms of transfusions by this time (ABC, TRICC studies already published) so more likely that sicker patients received the transfusions.

The evidence is basically non-inferior from a morbidity and mortality standpoint for the use of 7.0 g/dL and presence of symptoms as a transfusion trigger in medical patients without acute hemorrhage.

Update 2014: Holst et al performed a randomized, multicenter, parallel-group study (TRISS) in which patients with sepsis were randomized to transfusion triggers <9 g/dL or <7g/dL. In another demonstration that transfusion at a hemoglobin <7 g/dL in patients without active ischemia does not incur excess harm, the study found that 90 day mortality was not significantly different between the groups (43% <7 g/dL and 45% <9 g/dL).